Technical Field of the Invention
This invention relates to electric over-voltage and surge protection, and more specifically, to voltage surge protection of electrical circuits such as those used in railroad and other applications.
Description of the Related Art
Voltage excursions are frequently encountered which may damage or destroy sensitive electronic equipment and components. Examples of these voltage excursions are, but not limited to, electrical surges, voltage transients, over voltages, lightning energy, induced voltages, current surges, switching transients, etc. These will be referred to generally as electrical surges.
In a railroad installation which contains electrical equipment, such as a signal bungalow or enclosure, it is a common practice to protect critical electrical control circuits such as those controlling the track signals from electrical surges. These surges may be attributable to lightning or other known or unanticipated sources which create an unusually high voltage on the circuit. Surge protection is important because high voltage surges may destroy electrical components or contribute excessive electrical noise to a circuit causing it to malfunction or otherwise perform unpredictably.
To prevent damage from electrical surges, over-voltage or lightning arrestors are used to couple the energy from the circuit to ground when an electrical voltage surge is detected on the circuit exceeding a predetermined voltage with respect to a reference point. This effectively redirects the energy of the electrical surge to ground and protects the sensitive electrical circuit components. When it is necessary to protect more than one circuit, a surge arresting device is coupled to each circuit and attached to a ground bus. There may be several devices employed in this manner. The ground bus is then connected to an outside reference ground.